On 28/07/2022 16:15, Xenia Ragiadakou wrote:
On 7/28/22 16:56, Julien Grall wrote:
Hi,
On 28/07/2022 14:49, Xenia Ragiadakou wrote:
The macro parameter 'v' is used as an expression and needs to be
enclosed in
parentheses.
Signed-off-by: Xenia Ragiadakou <[email protected]>
---
xen/arch/arm/include/asm/arm64/sysregs.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/xen/arch/arm/include/asm/arm64/sysregs.h
b/xen/arch/arm/include/asm/arm64/sysregs.h
index 54670084c3..f5a7269a27 100644
--- a/xen/arch/arm/include/asm/arm64/sysregs.h
+++ b/xen/arch/arm/include/asm/arm64/sysregs.h
@@ -461,7 +461,7 @@
/* Access to system registers */
#define WRITE_SYSREG64(v, name) do { \
- uint64_t _r = v; \
+ uint64_t _r = (v); \
I am failing to see why the parentheses are necessary here. Could you
give an example where the lack of them would end up to different code?
Here v is supposed to be used as an expression. So maybe the rule wants
to enforce that in the macro we will pass an expression and not multiple
statements (?) ... not sure.
Do you mean something like below?
#include <stdio.h>
#include <inttypes.h>
#define foo(v) do { \
uint64_t _r = v; \
\
printf("_r %lu\n", _r); \
} while (0)
int main(void)
{
foo(1; printf("Bar\n"));
}
If yes, then I agree that the compiler will still be happy. Or if you
pass "1; 2", v would be set to 1 rather than 2. I am not sure why one
would want to write such code. But I guess we want to prevent that.
Cheers,
--
Julien Grall
